Updated XCode version tested, 6.4 is deprecated

.travis.yml

@@ -3,7 +3,7 @@ language: cpp
 matrix:
   include:
     - os: osx
-      osx_image: xcode6.4
+      osx_image: xcode7.3
       script:
         - cmake --version
         - mkdir ./build_unknown_release
@@ -15,7 +15,7 @@ matrix:
         - MATRIX_EVAL="INFO=C++unknown-release"
 
     - os: osx
-      osx_image: xcode6.4
+      osx_image: xcode7.3
       script:
         - cmake --version
         - mkdir ./build_pure_98_release
@@ -27,7 +27,7 @@ matrix:
         - MATRIX_EVAL="INFO=C++98-pure-release"
 
     - os: osx
-      osx_image: xcode6.4
+      osx_image: xcode7.3
       script:
         - cmake --version
         - mkdir ./build_pure_ms_release
@@ -39,7 +39,7 @@ matrix:
         - MATRIX_EVAL="INFO=C++98-pure-ms-release"
 
     - os: osx
-      osx_image: xcode6.4
+      osx_image: xcode7.3
       script:
         - cmake --version
         - mkdir ./build_pure_11_release
@@ -51,7 +51,7 @@ matrix:
         - MATRIX_EVAL="INFO=C++11-pure-release"
 
     - os: osx
-      osx_image: xcode6.4
+      osx_image: xcode7.3
       script:
         - cmake --version
         - mkdir ./build_sse2_11_release
@@ -111,7 +111,7 @@ matrix:
         - MATRIX_EVAL="INFO=C++14-avx-debug"
 
     - os: osx
-      osx_image: xcode10
+      osx_image: xcode11
       script:
         - cmake --version
         - mkdir ./build_pure_17_release
@@ -123,7 +123,7 @@ matrix:
         - MATRIX_EVAL="INFO=C++17-pure-release"
 
     - os: osx
-      osx_image: xcode10
+      osx_image: xcode11
       script:
         - cmake --version
         - mkdir ./build_pure_17_debug
@@ -135,7 +135,7 @@ matrix:
         - MATRIX_EVAL="INFO=C++17-pure-debug"
 
     - os: osx
-      osx_image: xcode10
+      osx_image: xcode11
       script:
         - cmake --version
         - mkdir ./build_avx_17_release
@@ -147,7 +147,7 @@ matrix:
         - MATRIX_EVAL="INFO=C++17-avx-release"
 
     - os: osx
-      osx_image: xcode10
+      osx_image: xcode11
       script:
         - cmake --version
         - mkdir ./build_avx_17_debug